NAICS (Network-Assisted Interference Cancellation and Suppression) is SI (Study Item) in LTE (Long Term Evolution) Rel.12 and targeted to realize advanced receiver to cancel/suppress interference in UE side by assistance of network signaling. The main task of NAICS SI is to investigate an enhanced receiver with network-assistant for mitigating the co-channel interference coming from inter-cell, intra-cell, or inter-stream.
In NAICS, with the help of eNB indication, an advanced receiver at UE could estimate the effective channel of the interference signal, demodulate the interference signal, and decode the interference signal. Accordingly, there are 3 types of NAICS receivers under discussion of 3GPP as follows: a) Interference suppression (IS) which can estimate the effective channel of the interference signal; b) Symbol-level interference cancellation (SLIC) which can estimate the effective channel of the interference signal and demodulate the interference signal; c) Codeword-level interference cancellation (CWIC) which can estimate the effective channel of the interference signal, demodulate the interference signal, and decode the interference signal. FIG. 1 illustrates a schematic diagram of the three types of NAICS receivers. The IS receiver comprises an effective channel estimator and a channel equalizer, the SLIC receiver comprises a demodulator in addition to the components of the IS receiver, and the CWIC receiver comprises a descrambler and a channel decoder supporting HARQ in addition to the components of the SLIC receiver.
Among the three types of receiver, SLIC, which needs only symbol-level interference information, is a good compromise between performance and complexity. The present disclosure focuses on SLIC receiver only. However, the present disclosure also applies to the IS receiver.
As an interference could be a dynamically scheduled signal of an interfering cell, such interference indication can be unicast indication of L1 (physical layer) signaling ((E)PDCCH) from a serving cell if backhaul is ideal. UE-specific information for each interferer (interfering UE), e.g. Resource Block (RB) allocation and MCS/PMI/RI (Modulation and Coding Scheme/Precoding Matrix Indicator/Rank Indication), should be indicated through L1 signaling. On the other hand, some long term information, such as cell-specific information, can be signaled by RRC (Radio Resource Control). For example, cell-specific information of an interfering cell, e.g. NeighCellsCRS-Info-r11 and CRS (Cell-Specific Reference Signal) power boosting factor (p-b), can be indicated in advance by RRC signaling.
In the interference indication, RB information occupies a large ratio of the bits used for the interference indication, especially for a wide bandwidth. Therefore, how to indicate RB information of interferer efficiently becomes an important issue.